Self-current induced spin-orbit torque in FeMn/Pt multilayers

TL;DR

This paper demonstrates that FeMn/Pt multilayers can generate significant spin-orbit torque without ultrathin ferromagnetic layers or external heavy metal layers, enabling efficient magnetization switching for practical spintronic devices.

Contribution

It introduces a multilayer structure that produces strong spin-orbit torque independently of total thickness, unlike traditional bilayers, expanding the potential for spintronic applications.

Findings

Spin-orbit torque effective field is about 4 times larger than NiFe/Pt bilayer.

Magnetization can be switched reversibly without external magnetic field.

Multilayers follow a three-dimensional Heisenberg model with finite Curie temperature.

Abstract

Extensive efforts have been devoted to the study of spin-orbit torque in ferromagnetic metal/heavy metal bilayers and exploitation of it for magnetization switching using an in-plane current. As the spin-orbit torque is inversely proportional to the thickness of the ferromagnetic layer, sizable effect has only been realized in bilayers with an ultrathin ferromagnetic layer. Here we demonstrate that, by stacking ultrathin Pt and FeMn alternately, both ferromagnetic properties and current induced spin-orbit torque can be achieved in FeMn/Pt multilayers without any constraint on its total thickness. The critical behavior of these multilayers follows closely three-dimensional Heisenberg model with a finite Curie temperature distribution. The spin torque effective field is about 4 times larger than that of NiFe/Pt bilayer with a same equivalent NiFe thickness. The self-current generated spin torque is able to switch the magnetization reversibly without the need for an external field or a thick heavy metal layer. The removal of both thickness constraint and necessity of using an adjacent heavy metal layer opens new possibilities for exploiting spin-orbit torque for practical applications.